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Oregon Forestsnail

Allogona

townsendiana

A member of the family Polygyridae (“land snails”) this species is one of the largest native terrestrial snails in BC. As with most snails, they are hermaphroditic (possessing both male and female sexual organs). Allogona male reproductive anatomy is unusual, from which the genus name meaning “different genitalia” is derived. Mating clusters of several individuals is not uncommon.

A “pulmonate” snail, this species have evolved their mantle cavity into a lung (instead of gills as still found in some snails). Breathing is through a single opening on the right side of the body which either remains open or opens and closes. One of the largest land snails in BC, the shell has 5 to 6 whorls (spirals) with lighter colored axial ribs (thin bands that cross each whorl). The uppermost whorls are often pale from wear. Shell colour ranges from gold to dark brown, lightening to amber around the aperture (shell opening). As the snail matures the shell can become bleached looking and begin to flake. This species lacks the ‘hairs’ found on the shell of other land snail species like the Pygmy Oregonian and Northwestern Hesperian. The thick white aperture lip of adult snails is evident when viewing the snail from below; juveniles lack this thickened aperture lip. Shell diameter 2.8-3.5 cm, shell diameter is 1.4 to 1.7 times shell height.

Download Species Fact Sheet in PDF

Status

Global Status:

G2G3

Provincial Status:

S2

SARA Status:

Endangered

BC List Status:

Red (Candidates for- Extirpated, Endangered, or Threatened status)

Similar Species

The large size, thick white shell aperture, and often bleached flaking appearance distinguish Oregon Forestsnail from most other land snails. Inexperienced observers will most likely confuse the introduced European Grove Snail (also called Brown-lipped Snail) which has become widely distributed especially in urban and rural areas of BC. Highly variable in shell colour and pattern, Grove Snail shells range from solid shades of dark brown or amber/yellow to shells with dark bands on yellow or grey. The closely related Puget Oregonian is almost the same size and also possesses a defined tooth on its shell aperture; but is believed to be extirpated from its historic range in BC. Pacific Sideband, though larger and more colourful, can have bleached, flaking shells as the snail matures. Northwest Hesperian, another native land snail is smaller (shell diameter <1.6 cm) and covered with short hairs, noticeable when the shell is held up to light. However these hairs can disappear with age. Many of these snail species can be found together so close examination is needed for proper identification.

Ecology

Range

Elevation: <350 m In B.C. Oregon Forestsnail is restricted to the Fraser Valley Lowlands and southeast Vancouver Island of the Coast Region. Occurrences range from both sides of the Fraser River, including: Langley, Chilliwack (Ryder Creek watershed, Little Mountain, Cheam Lake), Mission (Hatzic Prairie) and Abbotsford (McKee Peak and lower Sumas Mountain as well as the City proper). Populations have also been found at Colony Farm Regional Park in Coquitlam, historically near White Rock in the west, and near Hope in the east. The species is known from one location on southeast Vancouver Island (Crofton).
from where there are both historical (1903) and recent (2003) records.
Known occurrence on South Coast BC represented by the green dotted line and green stars

Habitat

On the South Coast BC, Oregon Forestsnail is found in broadleaf forests or mixed forests. The species is strongly associated with stands that support a mosaic of Bigleaf Maple, Western Redcedar, Red Alder, Salmonberry, Stinging Nettle, and Sword Fern (in the eastern Fraser Valley Pacific Waterleaf is often associated with OFS habitat). Oregon Forestsnail can be found on steep terrain as well as lowland sites and utilizes edge or transitional areas (“ecotones”). It generally requires intact, well-connected forested landscapes with high structural diversity and understory complexity that provide an essential microclimate for reproduction and hibernation. Patterns of distribution and abundance is poorly known. Even less is known about preferences for egg deposition sites or juvenile dispersal habitats which may vary across the range. Land snails are relatively sedentary and thought to have poor dispersal capabilities. Oregon Forestsnail can tolerate some level of disturbance but lacks necessary mobility to easily seek new undisturbed habitats. The species has been shown to utilize variable patch sizes from as little as 4 m2 to as large as 70 m2.Home range size however does not necessarily equate to the size and complexity of habitats needed to support a given population or populations. A thick leaf litter layer (5-10 cm) or moss layer is important for providing essential, moist microclimates that protect snails during cold temperatures and drought. Ground cover such as woody debris and rock piles provide additional foraging sites, areas for courtship and mating, summer refugia and winter hibernacula.

Diet

Oregon Forestsnail graze on and mulch herbaceous vegetation but appear to have a strong preference for Stinging Nettle, one of the plants populations are most often found in association with.

Life Cycle

Mating takes place during periods of high humidity (80-100%). Adults generally dig and deposit eggs in shallow nest holes in soft soil and leaf litter; nest holes may be shared. Oregon Forestsnail takes ~2-3 years to reach maturity and may live up to 5 years. While breeding is typically in the spring (March-April) egg deposition has been observed in November (Zevit 2016). Temperature and microclimate conditions likely play a key role.

Threats

Habitat loss and fragmentation due to urbanization, logging, and clearing.

High vulnerability to activities that impact microclimate conditions (e.g. moisture), decrease food supplies, and create barriers to dispersal (e.g. land clearing, extensive paved areas). Land snails have low tolerance to drying and exposure and poor disp

Possible competition from introduced species such as European Grove Snail and Brown Garden Snail.

Alteration of forage plant communities and microclimate conditions due to the introduced invasive and exotic plant species.

Conservation and Management

Apply conservation and management objectives as set-out in the “Recovery Strategy for the Oregon Forestsnail (Allogona townsendiana) in Canada (2016). Integrate complementary objectives, recommendations and assessment methods found in “Draft Gastropod Best Management Practices Guidebook Oregon Forestsnail and Other Land Snails at Risk in the Coastal Lowlands” 2010(found on the SCCP’ website). Where appropriate, measures as set out in the RISC Standards #40 “Inventory Methods for Terrestrial Arthropods” should be applied. Habitat suitability mapping as done for “Big Leaf Maple distribution for Puget Oregonian” found in the “Recovery Strategy for the Puget Oregonian Snail (Cryptomastix devia) in Canada” may also be a useful for Oregon Forestsnail. Oregon Forestsnail may occur under different habitat conditions than known, assessments may need to be conducted outside of the known habitat types and range.
This species is federally listed under the Species at Risk Act (SARA), habitat may be subject to protections and prohibitions under
the BC Wildlife Act and may also be governed under other provincial and federal regulations including the Fish Protection Act and
Federal Fisheries Act as well as Regional and local municipal bylaws.

The climate is changing rapidly, and terrestrial ectotherms are expected to be particularly vulnerable to changes in temperature and water regime, but also to an increase in extreme weather events in temperate regions. Physiological responses of terrestrial gastropods to climate change are poorly studied.

Our results suggest that the Oregon Forestsnail is a relatively sedentary species with limited dispersal ability in its adult stage. Although Oregon Forestsnails are likely unable to colonize suitable habitat independently, remnant forest–meadow mosaic patches such as our
study site provide valuable habitat for Oregon Forestsnail, which are supplementary to large tracts of intact forest where most of their populations are found. *Available by request from the authors through Research Gate

A source for authoritative conservation information on thousands of plants and animals and hundreds of ecological communities in BC. From here connect to all provincial and federal recovery plans (including the SARA Registry), COSEWIC (Committee on the Status of Endangered Wildlife in Canada), Identified Wildlife guidance and conservation requirements for specific species and ecological communities of conservation concern impacted by forestry activities) and links to E-Flora and E-Fauna (the Electronic Atlas of the Plants and Wildlife of British Columbia).

A joint venture resource providing comprehensive information on a range of species and ecological communities specific to the Coast Region of BC (including the South, Central and North Coast, Vancouver Island and Haida Gwaii).

Ovaska, K. and L. Sopuck. 2003. Inventory of rare gastropods in southwestern British Columbia. Report prepared by Biolinx Environmental Research Ltd. for BC Ministry of Water, Land and Air Protection, Victoria, BC.

Ovaska, K. and L. Sopuck. 2006. Surveys of potential Wildlife Habitat Areas for terrestrial gastropods at risk in southwest British Columbia, March 2006. Report prepared by Biolinx Environmental Research Ltd. for the Ministry of Environment, Victoria, BC.

Proulx, Gilbert et al. 2003. A Field Guide to Species at Risk in the Coast Forest Region of British Columbia. Published by International Forest Products and BC Ministry of Environment. Victoria (BC).

Credits

First edition prepared in 2010 by Pamela Zevit RPBio for the South Coast Conservation Program (SCCP) with Kristiina Ovaska and Lennart, Sopuck Biolinx Environmental, in partnership with: International Forest Products (Interfor), Capacity Forestry (CapFor). Original funding was made possible through the Sustainable Forestry Initiative (SFI) Revised 2015 by Isabelle Houde, RPBio in consultation with the SCCP.

2nd Edition 2014 by Isabelle Houde, RPBio in consultation with the SCCP. Content updated by the Pamela Zevit April 2017

Every effort has been made to ensure content accuracy. Comments or corrections should be directed to the South Coast Conservation Program: info@sccp.ca. Only images from “creative commons” sources (e.g. Wikipedia, Flickr, U.S. Government) can be used without permission and for non-commercial purposes only. All other images have been contributed for use by the SCCP and its partners/funders only.

Part of the National Conservation Plan, this project was undertaken with the financial support of the Government of Canada. Dans le cadre du Plan de Conservation National, ce projet a été réalisé avec l'appui financier du Gouvernement du Canada.

SOUTH COAST CONSERVATION PROGRAM

French translation of SCCP original content available upon request.

Images sourced from “creative commons” sources (e.g. Wikipedia, Flickr, U.S. Government) can be used without permission and for non-commercial purposes only. All other images have been contributed for use by the SCCP and its partners/funders only. Content on this site may not display correctly with older browsers. Updating to the latest version of your browser is recommended.